Method And Apparatus For Coding And Interleaving For Very High Throughput Wireless Communications

ABSTRACT

A wireless transmitter can include a plurality of bandwidth modules, each bandwidth module processing data based on a predetermined frequency band. In one embodiment, such a wireless transmitter can include encoding components for receiving transmit data and generating encoded data. A multiple-input multiple-output (MIMO) stream parser can receive the encoded data and generate a plurality of MIMO streams. A first module parser coupled to a first MIMO stream can generate a first plurality of partial MIMO streams. A first bandwidth module can include a first interleaver that interleaves bits of the first partial MIMO stream and generates first interleaved data. A second bandwidth module can include a second interleaver that interleaves bits of the second partial MIMO stream and generates second interleaved data. A first inverse fast Fourier transform (IFFT) unit can combine and process the first and second interleaved data and generate a first transmission MIMO stream.

RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.13/956,254, entitled “Method And Apparatus For Coding And InterleavingFor Very High Throughput Wireless Communications” filed Jul. 31, 2013,which is a continuation of U.S. patent application Ser. No. 13/245,776,entitled “Method And Apparatus For Coding And Interleaving For Very HighThroughput Wireless Communications” filed Sep. 26, 2011 which claimspriority of U.S. Provisional Patent Application 61/386,827, entitled“Method And Apparatus For Coding And Interleaving For Very HighThroughput Wireless Communications” filed Sep. 27, 2010.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates generally to communication systems and moreparticularly to wireless networks.

2. Related Art

Digital data can be transmitted over analog channels or wirelessly forcommunication to users. The channel over which data is communicated hasseveral inherent difficulties. Corruption of transmitted data occursadditively or multiplicatively due to noise and other physicalphenomena. A goal of the transmission and reception system is tocommunicate reliably and ably, despite these difficulties.

In order to communicate digital data over an analog channel, the data ismodulated using, among other techniques, a form of pulse amplitudemodulation. In pulse amplitude modulation (PAM), the amplitude of apulsed carrier changes based on the signal information. The signal oruseful information, therefore, is carried in the amplitude of the pulsesof the carrier. A form of pulse amplitude modulate is quadratureamplitude modulation (QAM). QAM is an improvement over a traditionalPAM, in that QAM increases the amount of data that can be transmittedwithin a particular channel. QAM is a form of PAM in which a pluralityof bits are transmitted in a constellation, that can contain, forexample 16 or 32 points. Typically, in a QAM, the signal changes both inthe amplitude dimension and the phase dimension.

A typical communication system over an analog channel or wirelesschannel involves a receiver and a transmitter. In order to handle thechannel uncertainty when the information is passed over the channel, theuseful information is encoded with redundant bits to correct single andmultiple bit errors as the information is received over the uncertainchannel. At the transmitter, the encoding for forward error correction(FEC) is performed. In order to reduce the probability of block errorsfrom occurring, the encoded information is passed over an interleaver,so that contiguous encoded bits are not transmitted adjacent to eachother. The symbols are then mapped over a carrier frequency in a bandthrough a form of frequency interleaving before being processed fortransmission. On reception, a reverse process is undertaken: thereceived data is de-interleaved and then decoded. The decoded data isprocessed for error detection and check, and if necessary, a correctionof data.

Typically, for a certain bandwidth and network architecture, a transmitdata path exists as a hardware implementation of all of the components.These components perform the functions of encoding, stream parsing, QAMmapping, OFDM modulation and preamble processing before passing theprocessed data to an RF transceiver connected to an antenna. On thereceive side, an antenna connected to an RF transceiver receives theinformation and subsequent components perform preamble processing, OFDMdemodulation, QAM de-mapping, bit de-interleaving and decoding. Bothreceive and transmit data paths have a certain data width and operate ata certain clock speed to support a certain bandwidth.

With the increase in the demands of the internet, all sections of thenetwork, including wireless LAN are going through a bandwidth explosion,necessitating an upgrade of the specifications to a higher bandwidth andwith better and more reliable performance. For an equipment vendor inthe networking area and particularly in the wireless LAN space, it isimperative to keep abreast with architectural changes driven by growthin demand for the bandwidth and develop products with reduced time tomarket and with competitive feature sets. For the vendors, it isincreasingly difficult to spin a new generation of product architecturewith each and every change in the specification.

In the evolutionary development of the 802.11 standard, the lateststandard is referred to as 802.11ac for “very high throughput” (VHT).VHT transfers data in a 5 GHz band. Embodiments include RF signalbandwidths of up to 160 MHz and data rates of up to 6.933 Gbps. In oneembodiment, maximum bandwidths can be 80 MHz or 160 MHz. More efficientsignal processing schemes and data path design techniques are beingdeployed to reduce noise and improve the signal to noise ratio alongwith scaling the bandwidths to double or quadruple the data transferrates.

Where a next generation network architecture with higher bandwidth is tobe supported, several trade-off points are available to the systemdesigner. The system designer performs under the constraints of managingrecurring and non-recurring engineering costs, reduced time to marketand faster adaptability to changing standards. There is no compromisehowever, on key aspects of supporting the higher specified bandwidth andmaintaining backwards compatibility to be able to work with equipmentthat has not yet been upgraded. The system designer's work invariablyinvolves a tradeoff between using the components designed for a previousgeneration and running it at same or higher speeds or redesigning theentire data path. Redesigning the entire data path presents substantialrisks to time to market. The new design has to be functionally verifiedand confirmed that it complies with a set of specifications forfunction, reliability, mechanics and environment, among others. Runningolder designs at higher speeds is not always feasible as the design hasbeen targeted to a certain clock speed for a certain target technology.

While some clock speedup is possible by way of upgrade of technology, itis not of the order of the scale by which the bandwidths are expandingfrom generation to generation. Further, where the design involves analogcomponents along with digital components, as in a silicon implementationof an RF radio receiver and transmitter, the linear scaling oftechnology is not possible, as it is for a purely digital design.Accordingly, traditional solutions do not present optimal solutions forthe system designer.

SUMMARY OF THE INVENTION

Various embodiments of the invention can provide a solution to thechallenges inherent in the design and implementation of wirelessdevices.

A wireless transmitter can include a plurality of bandwidth modules,each bandwidth module processing data based on a predetermined frequencyband. In one embodiment, such a wireless transmitter can includeencoding components for receiving transmit data and generating encodeddata. A multiple-input multiple-output (MIMO) stream parser can receivethe encoded data and generate a plurality of MIMO streams. A firstmodule parser coupled to a first MIMO stream can generate a firstplurality of partial MIMO streams. A first bandwidth module can includea first interleaver that interleaves bits of the first partial MIMOstream and generates first interleaved data. A second bandwidth modulecan include a second interleaver that interleaves bits of the secondpartial MIMO stream and generates second interleaved data. A firstinverse fast Fourier transform (IFFT) unit can combine and process thefirst and second interleaved data and generate a first transmission MIMOstream.

The first and second partial MIMO streams can be processed on adjacentor non-adjacent frequency bands. The first and second interleavers canadvantageously interleave the bits of the first and second partial MIMOstreams, respectively, over different frequency bands. In oneembodiment, the first module parser can allocate even bits of the MIMOstream to the first partial MIMO stream (for the first bandwidth module)and odd bits of the MIMO stream to the second partial MIMO stream (forthe second bandwidth module).

The wireless transmitter can further include a second module parsercoupled to a second MIMO stream from the MIMO stream parser. The secondmodule parser can generate a second plurality of partial MIMO streams.Notably, the first and second module parsers provide a same allocationof bits to the first and second bandwidth modules. The first bandwidthmodule can include a second interleaver that interleaves bits of a thirdpartial MIMO stream (from the second plurality of partial MIMO streams)and generates third interleaved data. The second bandwidth module caninclude a fourth interleaver that interleaves bits of a fourth partialMIMO stream (also from the second plurality of partial MIMO streams) andgenerates fourth interleaved data. A second IFFT unit, coupled to thethird and fourth bandwidth modules, can combine and process the thirdand fourth interleaved data to generate a second transmission MIMOstream.

In one embodiment, the first and second IFFT units each provide for a160 MHz bandwidth. The wireless transmitter can further include firstand second spatial mappers in the first and second bandwidth modules,respectively. Each of the first and second spatial mappers can receivemodulated, interleaved data and map tones to the first and second IFFTs.In one embodiment, each of the first and second spatial mappers performsmapping over 234 tones.

Another wireless transmitter described herein includes a module parserreceiving the transmit data and producing first and second data streamsfrom the transmit data. A first bandwidth module, coupled to the firstdata stream, can include first encoding components, a first MIMO streamparser, and a first interleaver. The first encoding component canreceive the first data stream and generate first encoded data. The firstMIMO stream parser can receive the first encoded data and generate afirst plurality of MIMO streams. The first interleaver can interleavebits of one of the first plurality of MIMO streams. A second bandwidthmodule, coupled to the second data stream, can include second encodingcomponents, a second MIMO stream parser, and a second interleaver. Thesecond encoding component can receive the second data stream andgenerate second encoded data. The second MIMO stream parser can receivethe second encoded data and generate a second plurality of MIMO streams.The second interleaver can interleave bits of one of the secondplurality of MIMO streams. The wireless transmitter can further includefirst and second IFFT units coupled to the first and second bandwidthmodules for processing interleaved data for transmission.

The first and second data streams are processed on adjacent ornon-adjacent frequency bands. In either embodiment, the first and secondinterleavers interleave bits of the first and second data streams overdifferent frequency bands. In one embodiment, the module parser canallocate even bits of the transmit data to the first data stream and oddbits of the transmit data to the second data stream. The wirelesstransmitter can further include first and second spatial mappers in thefirst and second bandwidth modules, respectively. Each of the first andsecond spatial mappers can receive modulated, interleaved data and maptones to the first and second IFFTs.

Another wireless transmitter described herein includes first and secondbandwidth modules and first and second IFFT units. Each of the bandwidthmodules can be configured to: receive a plurality of partial MIMOstreams including encoded transmit data, interleave bits of theplurality of partial MIMO streams to generate interleaved data, modulatethe interleaved data, and perform spatial mapping on the interleaveddata based on predetermined tones to generate mapped data. The first andsecond bandwidth modules can process the partial MIMO streams onadjacent or non-adjacent frequency bands. In one embodiment, the spatialmapping uses 234 tones for the predetermined tones. The first and secondIFFT units, which are coupled to the first and second bandwidth modules,can transform the mapped data for transmission.

The wireless transmitter can further include a MIMO stream parser and aplurality of module parsers. The MIMO stream parser can receive aplurality of encoded data streams and generate a plurality of MIMOstreams. Each module parser can receive a MIMO stream and allocate bitsof the MIMO stream to the first and second bandwidth modules based on apredetermined allocation scheme. In one embodiment, the predeterminedallocation scheme allocates even bits to the first bandwidth module andodd bits to the second bandwidth module.

Another wireless transmitter described herein includes first and secondbandwidth modules and first and second IFFT units in a differentconfiguration. Specifically, each of the first and second bandwidthmodules can be configured to: encode received transmit data to generateencoded data, parse the encoded data into first and second MIMO streams,interleave bits from each of the first and second MIMO streams togenerate interleaved bits, modulate the interleaved bits to generatemodulated data, and perform spatial mapping on the modulated data basedon predetermined tones (e.g. 234) to generate mapped data. The wirelesstransmitter can further include first and second IFFT units, coupled tothe first and second bandwidth modules, to transform the mapped data fortransmission. In one embodiment, the first bandwidth module can processits first and second MIMO streams on a first frequency band, whereas thesecond bandwidth module can process its first and second MIMO streams ona second frequency band. The first and second frequency bands can beadjacent or non-adjacent.

The wireless transmitter can further include a module parser for parsingthe received transmit data to the first and second bandwidth modulesbased on first and second frequency bands. The module parser isconfigured to parse based on a predetermined allocation scheme. In oneembodiment, the predetermined allocation scheme allocates a first set ofbits to the first bandwidth module and a second set of bits to thesecond bandwidth module, wherein the first and second sets of bits haveequal distribution.

BRIEF DESCRIPTION OF THE DRAWINGS

Various embodiments of the invention will be better understood from areading of the following detailed description, taken in conjunction withthe accompanying drawings in which like reference characters designatelike elements and in which:

FIG. 1 is a typical wireless LAN based network in a home or smallbusiness;

FIG. 2 is an exemplary high level block diagram of the physical layerimplementation of a radio frequency transmitter and receiver showingmajor functions from a data link layer source to a data link layer sinkand going through a wireless channel;

FIG. 3 is an exemplary diagram of an RF transmitter using quadratureamplitude modulation (QAM) and illustrating transmit physical layer withboth digital and analog components;

FIG. 4 is an exemplary diagram of the radio frequency (RF) receiverusing quadrature amplitude de-modulator and illustrating receivephysical layer with both digital and analog components;

FIG. 5 is an exemplary diagram illustrating a full bandwidth transmitdata path with encoding and interleaving occurring in a single block forthe entire 160 MHz band, in accordance with an embodiment of the presentinvention;

FIGS. 6A, 6B, and 6C are exemplary diagrams illustrating encoding andfrequency parsing in a consolidated fashion, with the interleavingfunction divided into two 80 MHz contiguous or non-contiguous bands, inaccordance with an embodiment of the present invention; and

FIGS. 7A and 7B are exemplary diagrams illustrating a modified data pathperforming encoding and interleaving in a divided fashion in each of thetwo halves of a full 160 MHz, in accordance with an embodiment of thepresent invention.

DETAILED DESCRIPTION OF THE DRAWINGS

Reference will now be made in detail to embodiments of the presentinvention, examples of which are illustrated in the accompanyingdrawings. While the invention will be described in conjunction with theembodiments, it will be understood that they are not intended to limitthe invention to these embodiments. On the contrary, the invention isintended to cover alternatives, modifications and equivalents, which maybe included within the spirit and scope of the invention as defined bythe appended claims. Furthermore, in the following detailed descriptionof embodiments of the present invention, numerous specific details areset forth in order to provide a thorough understanding of the presentinvention. However, it will be recognized by one of ordinary skill inthe art that the present invention may be practiced without thesespecific details. In other instances, well-known methods, procedures,components, and circuits have not been described in detail so as not tounnecessarily obscure aspects of the embodiments of the presentinvention. The drawings showing various embodiments of the invention aresemi-diagrammatic and not to scale and, particularly, some of thedimensions are for the clarity of presentation and are shown exaggeratedin the drawings. Similarly, although the views in the drawings for theease of description generally show similar orientations, this depictionin the drawings is arbitrary for the most part. Generally, embodimentsin accordance with the invention can be operated in any orientation.

Some portions of the detailed descriptions, which follow, are presentedin terms of procedures, steps, logic blocks, processing, and othersymbolic representations of operations on data bits within a computermemory. These descriptions and representations are the means used bythose skilled in the data processing arts to most effectively convey thesubstance of their work to others skilled in the art. A procedure,computer executed step, logic block, process, etc., is here, andgenerally, conceived to be a self-consistent sequence of steps orinstructions leading to a desired result. The steps are those requiringphysical manipulations of physical quantities. Usually, though notnecessarily, these quantities take the form of electrical or magneticsignals capable of being stored, transferred, combined, compared, andotherwise manipulated in a computer system. It has proven convenient attimes, principally for reasons of common usage, to refer to thesesignals as bits, values, elements, symbols, characters, terms, numbers,or the like.

It should be borne in mind, however, that all of these and similar termsare to be associated with the appropriate physical quantities and aremerely convenient labels applied to these quantities. Unlessspecifically stated otherwise as apparent from the followingdiscussions, it is appreciated that throughout the present disclosure,discussions utilizing terms such as “processing” or “accessing” or“executing” or “storing” or “rendering” or “receiving” or “producing” or“transforming” or “encoding” or “parsing” or interleaving” or the like,refer to the action and processes of a computer system, or similarelectronic computing device, that manipulates and transforms datarepresented as physical (electronic) quantities within the computersystem's registers and memories and other computer readable media intoother data similarly represented as physical quantities within thecomputer system memories or registers or other such information storage,transmission or display devices. When a component appears in severalembodiments, the use of the same reference numeral signifies that thecomponent is the same component as illustrated in the originalembodiment.

By way of example, and not limitation, computer-usable media maycomprise computer storage media and communication media. Computerstorage media includes volatile and nonvolatile, removable andnon-removable media implemented in any method or technology for storageof information such as computer-readable instructions, data structures,program modules or other data. Computer storage media includes, but isnot limited to, random access memory (RAM), read only memory (ROM),electrically erasable programmable ROM (EEPROM), flash memory or othermemory technology, compact disk ROM (CD-ROM), digital versatile disks(DVDs) or other optical storage, magnetic cassettes, magnetic tape,magnetic disk storage or other magnetic storage devices, or any othermedium that can be used to store the desired information.

Communication media can embody computer-readable instructions, datastructures, program modules or other data in a modulated data signalsuch as a carrier wave or other transport mechanism and includes anyinformation delivery media. The term “modulated data signal” means asignal that has one or more of its characteristics set or changed insuch a manner as to encode information in the signal. By way of example,and not limitation, communication media includes wired media such as awired network or direct-wired connection, and wireless media such asacoustic, radio frequency (RF), infrared and other wireless media.Combinations of any of the above should also be included within thescope of computer-readable media.

Various embodiments of the invention can provide a solution to theincreasing challenges inherent in wireless communications, such as withvery high throughput available with the 802.11ac standard. Variousembodiments of the present disclosure provide for the reuse of 80 MHzbandwidth modules in a 160 MHz bandwidth by dividing the 160 MHzbandwidth into an upper 80 MHz portion served by a first 80 MHzbandwidth module and a lower 80 MHz portion served by a second 80 MHzbandwidth module. Because subcarrier spacing is 312.5 kHz, the earlier802.11a standard, with a 20 MHz bandwidth, can provide 64 possibletones, and the 802.11n standard with a 20/40 MHz bandwidth can provideeither 64 or 128 possible tones. Therefore, the 802.11ac standard withan improved 20/40/80/160 MHz bandwidth can provide either 64, 128, 256or 512 possible tones. Such an increase in the number of total possibletones will allow a data stream to be more widely interleaved.Interleaving across 512 tones provides an improved performance with arobust dispersion of the data to prevent unrecoverable errors. Variousembodiments following the 802.11ac standard can involve, but are notlimited to, an 80 MHz bandwidth, and optionally may also utilize a 160MHz bandwidth. As described in detail below, two 80 MHz bandwidthmodules can be used in parallel to cover a full 160 MHz bandwidthprovided by the 802.11ac standard.

FIG. 1 illustrates a block diagram of a typical wireless LAN network100. Various embodiments can be deployed at for example a home orbusiness. Several users are represented by stations 130 among others.Stations 130 (STA1-STA5, in this embodiment) are capable of receivingand transmitting data from and to a base station 120. A wireless AccessPoint (AP) is one embodiment of the base station. The base station 120communicates with a router 115 through a wire or wirelessly. The router115 has network connectivity information on the network 100 and receivesand forwards packets based on the source and destination addresses. Arouter 115 has a plurality of ports for connections and a single uplinkport to connect to the rest of the internet through a cable modem 110,generally through a wire 160. A cable modem connects to the worldwideinternet through a Cable Modem Termination System (CMTS) located in acentral office of the service provider. Primarily, an embodiment dealswith the wireless communication 140 between a station 130 and basestation 120. The new 802.11ac VHT standard proposes to transport data atraw rates of up to 6.933 Gbps wirelessly and reliably over the air.

FIG. 2 illustrates the physical layer components of a transmitter and areceiver deployed in a station, access point or a router belonging to awireless LAN network 105 of the type described in FIG. 1. Generally,packet data having all of the layer two functions (in accordance withthe OSI communication model) and encapsulations is passed to thephysical layer through a source 210. To provide for security as well asto have a balanced number of ones and zeroes (wherein a balanced numberminimizes bias to the output signal), the packet data from the source210 passes through a scrambler 220. The output of the scrambler 220feeds into a coder 230, which encodes additional bits of information tobe able to perform error detection and correction. To this point, thepacket data based on layer two remains together. The error detection andcorrection function is effective where the number of errors in the blockover which the encoding has been performed remains low. Where multipleerrors do occur, which are not correctable by the use of forward errorcorrection (FEC), the packet has to be dropped. Where a packet is partof a larger data stream on a certain application, the whole stream needsto be dropped and retransmitted. To reduce the packet error rate, it isarchitecturally preferred that the packet localized data be distributedin both time and frequency to reduce the probability of localized packeterrors.

Such a distribution occurs through frequency interleaving and bitinterleaving. In frequency interleaving, where data is carried overcarrier buckets, the packetized data coming from layer two isdistributed over a number of buckets. This distribution is not dependenton the respective packet source of the data. Similarly, in bitinterleaving, the packet data from different packets are de-multiplexedto form a new stream with a mix of bits from a plurality of packets. Inone embodiment, this function is achieved by an interleaver block 240.The interleaved data passes through a quadrature amplitude modulation(QAM) mapper 250, which maps the interleaved stream into a constellationof symbols. Such QAM mapped data passes through an orthogonal frequencydomain modulator (OFDM), where the symbols from the QAM mapper aremapped onto carrier buckets in a certain band of operation. The outputof the demodulator feeds into a PHY block 270, which inserts thepreamble and performs additional processing on reception for channelestimation and frequency correction, among other things. The PHY block270 feeds into a radio frequency (RF) transmitter 280 (which forms partof an RF transceiver) to be transmitted over channel 290.

On the receive side, based on the antenna targeted, the transmittedinformation is received into an RF receiver 285 (which forms part of anRF transceiver), where the preamble is separated from the data of thepacket. The preamble is subject to additional receive processing inblock 275 before the preamble and the data are passed to an OFDMdemodulator 265. The OFDM demodulator 265 extracts bucket by bucket thedistributed information into a stream of symbols to be fed to a QAMde-mapper 255. The QAM de-mapper 255 converts the symbols into a streamthat is de-interleaved by block 245. The de-interleaved stream is thenpassed to a decoder 235 and a descrambler 225 before being passed to thedata link layer of the node through a sink 215.

Referring now also to FIG. 3, the transmitter path is described infurther detail, with some components of the transmitter digital pipe andthe analog components divided into their sub-components (some componentsof FIG. 2 are not shown for simplicity). The data link layer packetizedsource 210 feeds the data through the coder 230 and the interleaver 240to the QAM mapper 250. The OFDM modulator 260 can add pilot symbols tothe symbols generated by the QAM mapper 250 using a pilot symbolinsertion block 375. The resulting symbols are provided to an inversefast Fourier transform (IFFT) processor 330 where the guard and trainingsymbol insertion (in the preamble) is provided by a training symbolinsertion block 380 and a guard symbol insertion block 385 (wherein theOFDM modulator 260 can include the IFFT block 330, pilot symbolinsertion block 375, training symbol insertion block 380, and the guardinsertion block 385). The PHY block 270 can pass the IFFT block 330output through an interpolation filter 340, consisting of an up-samplerand a filter. The output of the interpolation filter 330 is provided toa digital to analog converter 350 (wherein the PHY block 270 can includethe interpolation filter 330 and the DAC 350). The RF transmitter 280can up convert the intermediate frequency output of the DAC 350 using anup converter block 355 before being amplified by amplifier 365 (bothforming part of the RF transmitter 280) and transmitted over an antenna395.

Referring now also to FIG. 4, the receiver path is described in furtherdetail, with some components of the receiver digital pipe and the analogcomponents divided into their sub-components (some components of FIG. 2are not shown for simplicity). The signal is received through an antenna405 and is fed to the RF receiver 285, which includes an amplifier 510for amplifying the received signal, and a down converter 415 for downconverting the amplified signal to an intermediate frequency 515. Thereceive processing block 275 receives the output of down converter 415and transforms the analog signal to a digital signal using an analog todigital converter (ADC) 420. The digital output from the ADC 420 isprocessed through a decimate filter synchronization block 425, whichalso forms part of receive processing block 275. The OFDM demodulator265 receives the output of the decimate filter synchronization block425. In this embodiment, OFDM modulator 265 can include a frequencycorrection block 430, a frequency error estimator 431, an FFT 432, apilot removal block 433, and a channel estimator block 434. Thefrequency correction block 430 receives the output of the decimatefilter synchronization block 425 as well as frequency error estimatesfrom the frequency error estimator 431, which processes pilots(identified by pilot removal block 433, in part using outputs from anFFT block 432) in the preamble of the frames to perform frequency errorestimation. The frequency-corrected signal is provided to an FFT block432, which outputs its processed signal to the QAM demodulator 255.Channel estimator 434 also uses the identified pilots from the pilotremoval block 433 to compute channel estimations, which are then alsoprovided to the QAM demodulator 255. The output of the QAM demodulator255 is fed to a de-interleaver 245 and the decoder 235 to pass theprocessed data to the sink 215, thereby signifying passage of packetdata to the data link layer.

In an embodiment of the present invention, among other things,architectural tradeoffs are made in the delineation of functions andplacement of the encoder 415, interleaver 425 and their receivecounterparts, decoder 565 and de-interleaver 555.

FIG. 5 builds upon the transmit data path of FIG. 3 to provide a nextgeneration transmit data path, designed for a wider band (e.g. 80 MHz to160 MHz). The source of data in FIG. 5 may be the data link layer, whichpresents packet localized data. A scrambler 510 can scramble this data.The scrambled data stream is then parsed by an encoder parser 520 todivide the packetized data into modular elements over which a forwarderror correction (FEC) protocol can be executed by a plurality of FECblocks 530. The encoder parser 520 may be used when some coding, such asa convolutional coding, may be desired. In some embodiments, the encoderparser 520 may be omitted when a Low Density Parity Check (LDPC) isemployed elsewhere in the processing of the transmit data path. In oneembodiment, the encoder parser 520 may parse an incoming data stream ina bit-wise or block wise round robin fashion.

The FEC blocks 530 may encode the stream of data with any common forwarderror correction coding. Typically such coding adds additional data(additional bits, in some cases) to allow a receiver to correct receiveor transmission errors. In one embodiment, the entire effective datalink layer is encoded across the complete bandwidth. The outputs of theFEC blocks 530 are streamed to a multiple-input multiple-output (MIMO)stream parser 540 to feed data into multiple, parallel MIMO streams forQAM mapping. In this embodiment, the MIMO stream parser 540 parses thedata from the FEC blocks 530 into two MIMO streams. In otherembodiments, the MIMO stream parser 540 may parse the stream into threeor more MIMO streams. In yet other embodiments, the MIMO stream parser540 may be bypassed when only one MIMO stream (i.e. one path of QAMmapping) is to be used. The number of MIMO streams in any particularembodiment may be a design choice. The MIMO stream parser 540 may parsebits in a round-robin bit-wise fashion. In alternative embodiments, theMIMO stream parser 540 may parse groups of bits in a round-robinfashion, or in any random or pseudo-random fashion.

The output of the MIMO stream parser 540 is coupled to interleaverblocks 550 and 555. Interleaver blocks 550 and 555 may use anywell-known interleaving method. In one embodiment, an interleaver may beimplemented with memory. Incoming data may be written into rows of thememory while outgoing data may be read out of columns of the memory. Inone embodiment, data is interleaved across the entire band of interest.Interleavers 550, 555 may be coupled to QAM mappers 560 and 565,respectively. In some embodiments, the output of a QAM mapper may becoupled to a cyclic shift delayer (CSD), which may help preventunintentional beamforming. In one typical embodiment, all MIMO streams,with the exception of one MIMO stream, include CSD blocks.

In FIG. 5, the two MIMO streams (one from QAM mapper 560 and one fromCSD 558) are coupled to a spatial mapper 570. The spatial mapper 570 maydetermine how data from the QAM mapper 560 and the data from the CSD 558are distributed to the transmission MIMO streams. In this embodiment,the spatial mapper 570 maps data to two transmission MIMO streams, whichare coupled to IFFTs 580 and 585. The outputs of the IFFTs 580 and 585are coupled to DACs 590 and 595, respectively. Note that when thetransmission is to occur over two non-adjacent 80 MHz bands (e.g.,non-contiguous transmission), then the output of the spatial mapper 570may increase the number of transmission MIMO streams. For example, thetwo transmission MIMO streams shown in FIG. 5 may be split further intofour transmission MIMO streams, with each transmission MIMO streamhaving a separate IFFT and DAC.

As configured in FIG. 5, a single flow data path is used for the entireexemplary 160 MHz band of operation. In this example, the implementationmay use 468 tones (i.e., frequency bins) to cover 160 MHz (for example,512 tones less 44 tones accounting for pilot, DC, and guard tones). Assuch, the interleavers 550 and 555 operate to interleave 468 tones andthe IFFT may likewise operate on 512 tones spread over 160 MHz. Thus, asshown in FIG. 5, two streams may each be coded with 512 point IFFTs (580and 585), each occupying the same frequency space. This solution isoptimal for performance, as there is a natural match between the datapath and the architectural requirements. Also, the entire 160 MHzbandwidth is available for frequency interleaving and bit interleaving.Due to more possibilities of interleaving in both bit and frequencydimension, the packet error rate can be low. This solution requires,however, that the hardware of the frequency domain functions run twiceas fast as compared to other implementations because the data path mustprocess all 468 tones. As more tones are provided, the data stream mustbe interleaved over a greater number of tones for a given time interval,requiring the system to run faster.

As noted above, the proposed IEEE 802.11ac standard requires an 80 MHzbandwidth, with a 160 MHz bandwidth optional. Therefore, a minimum 80MHz bandwidth module is required for operation. In one exemplaryembodiment, a pair of the 80 MHz bandwidth modules can be pairedtogether to provide a 160 MHz bandwidth. An embodiment utilizing a pairof 80 MHz bandwidth modules, rather than a single 160 MHz module, maybenefit from having each bandwidth module handle only 256 possible tonesrather than the full 512 tones, thereby allowing for a slower clockspeed. However, the interleavers in the 80 MHz bandwidth modules mayonly operate across half of the full 160 MHz bandwidth, which can reducethe performance of the device. Less interleaving can result in feweropportunities to prevent unrecoverable errors. However, as discussedbelow, embodiments of the present invention provide a good tradeoffbalance between performance and hardware complexity.

FIG. 6A illustrates an exemplary data path solution for 160 MHzbandwidth operation. Exemplary embodiments can transmit data over anentire 160 MHz bandwidth using two or more modules. By way of theexample of FIG. 6A, data from the link layer is transmitted with twobandwidth modules 601A and 601B. The bandwidth modules 601A and 601B maybe relatively similar and process data for the entire band of interestby splitting the processing work relatively evenly to both bandwidthmodules.

The data from the data link layer is passed through a scrambler 610, anencoder parser 620, forward error correction blocks 630, and a streamparser 640. The encoder parser 620 may operate relatively similar to theencoder parser 520 (FIG. 5). In one embodiment, the MIMO stream parser640 generates two MIMO streams that are provided to module parsers 646and 648. The output bits of each module parser are allocated to the twobandwidth modules 601A and 601B in a predetermined manner. For example,the even bits may be allocated to a first bandwidth module 601A and theodd bits may be allocated to a second bandwidth module 601B, as shown inFIG. 6B. In other embodiments, for each stream, the module parser outputbits are allocated to two bandwidth modules in a block-wise alternatingfashion. In yet other embodiments, for each stream, the module parseroutput bits are allocated to two bandwidth modules in a random orpseudo-random fashion.

Thus, in this embodiment, module parsers 646 and 648 divide each MIMOstream into two partial MIMO streams, each processing a portion of theoriginal frequency band. For example, an original 160 MHz stream may besplit into two 80 MHz streams (each bandwidth module handling 80 MHz).Interleaving as provided by interleavers 650 and 655 may be as describedfor interleavers 550 and 555 (FIG. 5). In this embodiment, interleavingoccurs within each bandwidth module. In addition to interleavers 650,655, quadrature amplitude mappers 660, 665 and a cyclic shift delay 668are also provided, along with the spatial mapper 670 in each ofbandwidth modules 601A and 601B. Each of bandwidth modules 601A and 601Binterfaces with IFFT blocks 680, 685, which in turn interface with DACs690, 695. In one embodiment of FIG. 6, IFFTs 680, 685 and DACs 690, 695may operate together to cover an entire frequency band of interest.Thus, both IFFTs cover the same band of interest. Although each ofbandwidth modules 601A and 601B may only operate with half of the entirenumber of tones required to cover a band of interest (i.e., 234 tones),the tones from both bandwidth modules 601A and 601B may be combined bythe IFFTs 680, 685 to cover the entire band of interest.

Note that in this configuration, each IFFT and DAC pair can supportseparate bands wherein each band may be non-adjacent or adjacent to itsnearest band. Thus, the spatial mappers 670 may be modified such thatpartial MIMO streams may be mapped into particular frequency bands. Forexample, if a 512 point IFFT is replaced by two 256 point IFFTs, thenessentially two independent frequency bands may be transmitted.Following this example, if the 512 point IFFT serviced 160 MHz, then two256 IFFTs may service two 80 MHz bands. These bands need not be adjacentto each other in frequency. Furthermore, each band may use anindependent modulation scheme from the other.

As noted above, the configuration of FIG. 6A allows coding by the FEC630s to code over the entire band of interest. Interleaving, on theother hand, is only spread over a portion of the band of interest by wayof the bandwidth modules. In FIG. 6A, interleavers 650 and 655 operateover a first portion of the band of interest, while correspondinginterleaver blocks in the bandwidth module 601B operate over a secondportion of the band of interest.

The design approach shown in FIG. 6A may have reduced design risks sincelower clock speeds may be required by virtue of splitting work acrosstwo or more bandwidth modules. It can be appreciated that the encodingin this embodiment of the invention occurs outside of the replicatedmodules and hence across the entire band. Therefore, the ability todetect and correct errors remains robust as the data stream isdistributed to the replicated paths after encoding, maintaining almostthe same number of redundant bits and frequency interleavingpossibilities as the solution of FIG. 5. Simulation results have shownsome degradation in performance, but for the packet error rate to bewithin 10% of the solution in FIG. 5, only 0.2 decibels of additionalsignal to noise ratio is required for the embodiment illustrated in FIG.6A. In this embodiment of the present invention, nearly as good aperformance as from FIG. 5 (full data path design for 160 MHz bandwidth)is obtained along with the ability to share components from previousdesign cycles, reducing time to market and making possible the avoidanceof a design and verification cycle.

Although FIG. 6A shows only two bandwidth modules 601A and 601B, otherembodiments may use three or more bandwidth modules. Interleaving stillonly occurs within each bandwidth module, but since coding by FECmodules occurs upstream of bandwidth modules, coding still is spreadacross the entire band of interest. Furthermore, although FIG. 6A showsthe case of two bandwidth modules supporting identical bandwidths, otherembodiments may use bandwidth modules where each bandwidth modulesupports different bandwidths.

Note that the entire frequency band of interest may not be continuous.That is, the frequency band that may be selected for transmission may becomprised of separate, non-adjacent frequency bands. To support thisconfiguration, additional IFFTs and corresponding DACs can be included,as shown in FIG. 6C. For example, IFFTs 680, 685 and DACs 690, 695 canbe replaced by IFFTs 680A, 680B, 685A, 685B and DACs 685A, 685B, 695A,695B. In one embodiment, the IFFTs 680A, 680B, 685A, 685B can receiveindependent outputs from the spatial mappers 670 in bandwidth modules601A and 601B. Moreover, IFFTs 680A, 685A can be 262 point IFFTsdirected to frequency band F1, whereas IFFTs 680B and 685B can be 262point IFFTs directed to frequency band F2. Note that although four IFFTsand DACs are shown, any even number of IFFTs/DACs can be used to processhalf the number of frequency bands (e.g. 4 IFFTs/DACs for 2 frequencybands, 6 IFFTs/DACs for 3 frequency bands, etc.). In one embodiment, thefrequency bands are not the same bandwidth, e.g. one set of thefrequency bands could be directed to 40 MHz and another set of thefrequency bands could be directed to 20 MHz (thereby not using the full160 MHz bandwidth).

FIG. 7A illustrates another exemplary embodiment of the presentinvention. The data link layer traffic is passed through a scrambler710. In this case, however, the next block is the module parser 720 thatsplits the data stream into two streams prior to the encoding functionperformed by a encoder parser 730, which occurs in both bandwidthmodules 701A and 701B. The module parser 720 may function similarly tothe module parsers 646 and 648 (FIG. 6B), as shown in FIG. 7B. Incontrast to FIG. 6A, each of the bandwidth modules 701A and 701Bincludes an encoder parser 730 and an FEC 740. After encoding by encoderparser 730 and FEC 740, a stream parser 746 can create a plurality ofMIMO streams. In the embodiment of FIG. 7A, interleavers 750, 755, QAMs760, 765, and CSD 767 can process the two MIMO streams in each ofbandwidth modules 701A and 701B. A spatial mapper 770 can combine thetwo MIMO streams and then map the resulting stream into an appropriatenumber of transmission MIMO streams. IFFTs 780, 785 and DACs 790, 795can process the combined MIMO streams from bandwidth modules 701A, 701B.

As shown in FIG. 7A, the IFFTs 780, 785 may operate on 512 tones similarto the IFFTs described in FIG. 6. Similar to the configuration describedfor FIG. 6C, the data from the spatial mapper 770 may be mapped to twoor more adjacent or non-adjacent frequency bands by replacing, forexample, an IFFT with two or more IFFT blocks (and corresponding DACs).For example, if 512 point IFFT 780 is replaced with two 256 point IFFTs,then the streams could be mapped to the 256 point IFFTs wherein eachIFFT (and corresponding DAC) may process data for a frequency band.Since each IFFT is independent, the frequency bands can also beindependent (i.e. the frequency bands need not be adjacent).Furthermore, signals transmitted on independent frequency bands may beindependently encoded with different modulate and coding scheme (MCS).

The data stream in this exemplary design is frequency parsed beforeencoding. Therefore, a degree of mix within each replicated data path islimited. Encoding and interleaving occur substantially within eachbandwidth module. Accordingly, a packet error rate (PER) for theembodiment in FIG. 7A may be higher than a packet error rate (PER) forthe embodiments in FIG. 5 and FIG. 6A. Simulation results done undersimilar conditions to the simulations done for the embodiment of FIG. 6Amay establish this. Whereas the solution of FIG. 6A may require only 0.2dB of additional signal to noise ratio to be within 10% of the packeterror rate of the exemplary embodiment illustrated in FIG. 5, theexemplary embodiment illustrated in FIG. 7A may require an improvementin the signal to noise ratio of 1-1.5 dB for some of the modulation andcoding schemes. However, the scheme of FIG. 7A has an advantage ofsharing the encoding function within the bandwidth module.

Other embodiments of FIG. 7A may include three or more bandwidthmodules. In addition, other embodiments of FIG. 7A may support bandwidthmodules in which each bandwidth module may support different bandwidths.

It can be noted by artisans skilled in the art that whereas thissolution of delineating coding and interleaving functions on a transmitdata path has been shown for a wireless LAN application, the samesolution or an embodiment of the present invention may be similarlyapplied to other forms of QAM applications. These include point to pointQAM applications with 16, 32, 64, 128 and 256 constellations. Otherapplications include but are not restricted to a digital videotransmitter and receiver with 16, 32 or 64 QAM and cable TV with 16, 64and 256 QAM.

It can also be appreciated that while a transmitter has been proposed indetail, through description and illustration of FIGS. 5, 6A, 6B, 7A, 7B,a similar and a symmetric scheme applies to the receive path, withblocks replaced with their corresponding blocks from the receive pipeillustrated in FIG. 4. For the communication to work in each of thethree schemes, the receive path is analogous as regards to there beingno replication, replication with decoding, and replication withoutdecoding. This is exactly similar to the transmit path. Architecturally,those skilled in the art can recognize that the design of thetransmitter also controls the design of the receiver.

An embodiment of the present invention includes a complete data linksource to data link sink system path as illustrated in FIG. 1, withportions of the receiver and transmitter functionally specified inaccordance with FIGS. 5, 6A, 6B, and FIGS. 7A, 7B for the transmitterand analogous functions for the receiver. In one embodiment of thepresent invention, the solution of FIG. 6A is a preferred embodiment ofthe design.

Although certain embodiments have been disclosed herein, it will beapparent from the foregoing disclosure to those skilled in the art thatvariations and modifications of such embodiments may be made withoutdeparting from the spirit and scope of the invention. It is intendedthat the invention shall be limited only to the extent required by theappended claims and the rules and principles of applicable law.

1. A method of wireless transmission comprising: generating encoded datain response to received transmit data; parsing the encoded data toprovide a plurality of multiple-input multiple-output (MIMO) streams;parsing a first MIMO stream of the plurality of MIMO streams to providea first plurality of partial MIMO streams, including a first partialMIMO stream and a second partial MIMO stream; interleaving bits of thefirst partial MIMO stream to provide first interleaved data;interleaving bits of the second partial MIMO stream to provide secondinterleaved data; and performing a first inverse fast Fourier transform(IFFT) based on both the first and second interleaved data to generate afirst transmission MIMO stream.
 2. The method of claim 1, furthercomprising processing the first and second partial MIMO streams onadjacent frequency bands.
 3. The method of claim 1, further comprisingprocessing the first and second partial MIMO streams on non-adjacentfrequency bands.
 4. The method of claim 1, further comprising:interleaving bits of the first partial MIMO stream over a firstfrequency band; and interleaving bits of the second partial MIMO streamover a second frequency band, different than the first frequency band.5. The method of claim 1, wherein parsing the first MIMO stream toprovide the first plurality of partial MIMO streams comprises:allocating even bits of the first MIMO stream to the first partial MIMOstream; and allocating odd bits of the first MIMO stream to the secondpartial MIMO stream.
 6. The method of claim 1, further comprising:parsing a second MIMO stream of the plurality of MIMO streams to providea second plurality of partial MIMO streams, including a third partialMIMO stream and a fourth partial MIMO stream, wherein a same allocationof bits is used to provide the first and second pluralities of partialMIMO streams; interleaving bits of the third partial MIMO stream toprovide third interleaved data; interleaving bits of the fourth partialMIMO stream to provide fourth interleaved data; and performing a secondinverse fast Fourier transform (IFFT) based on both the third and fourthinterleaved data to generate a second transmission MIMO stream.
 7. Themethod of claim 6, wherein the first and second IFFT each provide for a160 MHz bandwidth.
 8. The method of claim 6, further comprising:modulating the first, second, third and fourth interleaved data toprovide first, second, third and fourth modulated data, respectively;performing spatial mapping based on the first and second modulated data,thereby providing tones for performing the first IFFT; and performingspatial mapping based on the third and fourth modulated data, therebyproviding tones for performing the second IFFT.
 9. The method of claim8, wherein the spatial mapping is performed over 234 tones.
 10. Awireless transmitter comprising: means for generating encoded data inresponse to received transmit data; means for parsing the encoded datato provide a plurality of multiple-input multiple-output (MIMO) streams;means for parsing a first MIMO stream of the plurality of MIMO streamsto provide a first plurality of partial MIMO streams, including a firstpartial MIMO stream and a second partial MIMO stream; means forinterleaving bits of the first partial MIMO stream to provide firstinterleaved data; means for interleaving bits of the second partial MIMOstream to provide second interleaved data; and means for performing afirst inverse fast Fourier transform (IFFT) based on both the first andsecond interleaved data to generate a first transmission MIMO stream.11. The wireless transmitter of claim 10, wherein the first and secondpartial MIMO streams are processed on adjacent frequency bands.
 12. Thewireless transmitter of claim 10, wherein the first and second partialMIMO streams are processed on non-adjacent frequency bands.
 13. Thewireless transmitter of claim 10, further comprising: means forinterleaving bits of the first partial MIMO stream over a firstfrequency band; and means for interleaving bits of the second partialMIMO stream over a second frequency band, different than the firstfrequency band.
 14. The wireless transmitter of claim 10, wherein themeans for parsing the first MIMO stream to provide the first pluralityof partial MIMO streams comprises: means for allocating even bits of thefirst MIMO stream to the first partial MIMO stream, and allocating oddbits of the first MIMO stream to the second partial MIMO stream.
 15. Thewireless transmitter of claim 10, further comprising: means for parsinga second MIMO stream of the plurality of MIMO streams to provide asecond plurality of partial MIMO streams, including a third partial MIMOstream and a fourth partial MIMO stream, wherein a same allocation ofbits is used to provide the first and second pluralities of partial MIMOstreams; means for interleaving bits of the third partial MIMO stream toprovide third interleaved data; means for interleaving bits of thefourth partial MIMO stream to provide fourth interleaved data; and meansfor performing a second inverse fast Fourier transform (IFFT) based onboth the third and fourth interleaved data to generate a secondtransmission MIMO stream.
 16. The wireless transmitter of claim 15,further comprising: means for modulating the first, second, third andfourth interleaved data to provide first, second, third and fourthmodulated data, respectively; means for performing spatial mapping basedon the first and second modulated data, thereby providing tones forperforming the first IFFT; and means for performing spatial mappingbased on the third and fourth modulated data, thereby providing tonesfor performing the second IFFT.